The testing of respirators and/or protective masks often utilizes a “head form” upon which the respirator or mask is mounted. Head forms often utilize a compliant mask registration member to interface with the respirator under test and to provide a positive seal against the seal cushion or interface seal of the respirator mask that seats against the user's face. The mask registration member can enable the use of a single head form to test respirators or masks of various sizes and having different interface sealing contours.
An inflatable “bladder” is commonly used as the mask registration member. The inflatable bladder conforms to the general shape of the interface seal to provide a seal between head form and mask. Accordingly, any leaks detected are generally known to originate with the mask components rather than with the mask fit.
U.S. Pat. No. 5,808,182 to Stumpf, the disclosure of which is hereby incorporated by reference herein in its entirety except for terms expressly defined therein, discloses a “covering” that covers a portion of a head form and is inflatable through a port on the head form. The covering of Stumpf comprises a wide, flexible band with transitions areas near the edges of the band that are sealed against the head form. Accordingly, the transition area must be constructed pressure tight to guarantee inflation of the covering. Stumpf does not disclose how these transition areas are to be made pressure tight.
U.S. Pat. No. 7,343,783 to Tilley, which is also hereby incorporated by reference herein in its entirety except for terms expressly defined therein, discloses an “inflatable seal” that is disposed in a recess on a single portion of a head form. Tilley offers no details on the construction of the inflatable seal, nor how the inflatable seal is secured within the recess. However, an embodiment of the Tilley disclosure is commercially available as part of the TDA-99B Respirator Function Tester, marketed by Air Techniques International of Owings Mills, Md., USA. The inflatable seals used in the TDA-99B comprise a seam that is sealed with an adhesive, and also an inlet tube that is inserted through an opening or slit in the inflatable seal and sealed using a patch and adhesive. The adhesives in the inflatable seal of the TDA-99B necessitates additional curing time in the manufacturing of the inflatable seal, and also additional quality assurance steps to check the integrity of the inflatable seal and the inlet tube.
Various components of a respirator test system require periodic calibration and maintenance to assure competent results. Such calibration and maintenance can require removal of the individual sensors, shipping of the test unit, or switching equipment and/or test fixtures to accommodate field calibration that adds to the bulk of the respirator test system.
U.S. Pat. No. 8,312,761, assigned to the assignee of the present application, discloses a head form having a bladder member that can be assembled to form an inflatable bladder without the use of adhesives and is suitable for replacement in the field. In one embodiment, the bladder member includes a pair of flanges that are disposed in a recess between a face portion and a base portion of the head form. The recess and flanges are dimensioned to cause an interference fit between the head form and the bladder member to compress the flanges together and secure the bladder member in place upon assembly. The compression causes the flanges to seal against each other for a leak tight fit. Also, sealing members, such as O-rings, can be disposed on the face and base portions, respectively, within the recess, to seal between the exterior of the flanges and the head form.
At higher inflation pressures, it has been observed that the inflatable bladder described in U.S. Pat. No. 8,312,761 can lift partially out of the recess in a phenomenon referred to herein as “lift away.” Lift away can cause the flanges to slip beyond the seals in the recess and/or to deform with respect to each other and the inner surfaces of the recess, causing leaks in the head form assembly. Also, portions of the inflatable bladder that register against the head form can deform or curl away from the head form in a phenomenon herein referred to as “roll away.” Roll away can cause the surface of the inflatable bladder against which the mask registers to take on a fundamentally different shape, which can cause leaks between the interface seal and the inflatable bladder.
At higher inflation pressures, it has been observed that the inflatable bladder described in the '049 Application can lift partially out of the recess in a phenomenon referred to herein as “lift away.” Lift away can cause the flanges to slip beyond the seals in the recess and/or to deform with respect to each other and the inner surfaces of the recess, causing leaks in the head form assembly. Also, portions of the inflatable bladder that register against the head form can deform or curl away from the head form in a phenomenon herein referred to as “roll away.” Roll away can cause the surface of the inflatable bladder against which the mask registers to take on a fundamentally different shape, which can cause leaks between the interface seal and the inflatable bladder.
Also, it has been observed that leaks will occasionally occur between the interface seal and the bladder even after inflation, and particularly when the bladder is new. The leaks cause a false positive that the mask components are leaking.
Organizations involved in the testing of respirators would welcome a respirator test accessory that complements already existing aerosol detection equipment and eases the burdens on equipment and personnel with respect to calibration and maintenance. Manufacturers of such test accessories would welcome an assembly process that reduces the dependence on adhesive seals and the time and quality assurance testing attendant thereto. Embodiments that address the problems of false positives of mask leakage, bladder lift away and/or bladder roll away would also be welcome.